Overarch

Overarch provides an ontology and a data driven model of software systems and organizations based on e.g. UML and the C4 model.

Model your system as data and specify/generate representations (e.g. diagrams) for your system. All core and supplementary C4 diagrams except code diagrams are supported. Also UML use case, state machine and class diagrams are supported.

Overarch is not so much about how to model your architecture (see C4 Model for that), but about making these models composable and reusable.

Features

• Models to capture architecture on different levels
  • Concepts, use cases, architecture, state machines, code, deployments, organization structures and processes
• Models and views as data
• Separation of model and views
• Models are queriable, extensible, composeable and reusable
• View specific customization of model elements
• Criteria based model queries
• Template based artifact generation for e.g.
  • Documentation, reports, project templates, code, CI/CD pipelines, custom visualizations
• Diagram generation
  • PlantUML
    • All C4 views, use case, state machine and code diagrams, structure diagrams for organizations, systems and deployments
    • Styling and sprite support
  • GraphViz
    • Concept maps
    • Model view of all elements
• Model exports
  • JSON if you need to process models with languages without EDN support
  • Structurizr experimental
• Watch model directories for changes

Rationale

UML and C4 models are great to model and vizualize an architecture on different levels of detail with the various diagrams types. The value lies in an expressive description and visualization of an architecture with different views.

But the models used for diagram generation with the existing diagram tools are not models in the sense of generality. E.g. if you describe your model in PlantUML files, these descriptions are mere textfiles. These textfiles don't compose and you can't do anything else with these descriptions other than render them with PlantUML. The parsing process is opaque and you don't have access to the data of the model. Also the model is complected with the diagrams, as layout and rendering information is part of the model description and vice versa. The model should capture the essence of the architecture and not its representation.

If the model is described as plain data in an open format, it can be transformed into a graphical representation, e.g. into PlantUML textfiles, via the specification of views on the model.

In Overarch the model data is separated from information about these representations. Models can be composed with these views and with other models. By doing so, the model may also be used in other ways, e.g. the generation of documentation, code or infrastructure.

Even if the model is specified as data, the format is a text file (EDN, JSON) to be easily edited with text editors by the whole team and to be committed to version control, instead of being in some propriatory binary format.

The native format is the Extensible Data Notation (EDN) with representations in other formats like JSON. EDN is a textual format for data, which is human readable. It is also directly readable into data structures in clojure or java code. The data format is also open for extension. E.g. it copes with additional attributes or element types in the data structures.

Example

This is an example of the specification of a model and some diagrams based on the Internet Banking System example of Simon Brown at C4 Model.

The complete model and diagram specifications can be found under models/banking.

Further information about modelling with Overarch can be found in Usage.

Example of a model definition

#{; actors
  {:el :person
  :id :banking/personal-customer
  :name "Personal Banking Customer"
  :desc "A customer of the bank, with personal banking accounts."}
 ; system under design
{:el :system
 :id :banking.internet-banking/internet-banking-system
 :name "Internet Banking System"
 :desc "Allows customers to view information about their bank accounts and make payments."
 :ct #{{:el :container
        :id :banking.internet-banking/web-app
        :name "Web Application"
        :desc "Deliveres the static content and the internet banking single page application."
        :tech "Clojure, Luminus"}
       {:el :container
        :id :banking.internet-banking/single-page-app
        :name "Single-Page Application"
        :desc "Provides all of the internet banking functionality to customers via their web browser."
        :tech "ClojureScript, Re-Frame"}
       {:el :container
        :id :banking.internet-banking/mobile-app
        :name "Mobile App"
        :desc "Provides a limited subset of the internet banking functionality to customers via their mobile device."
        :tech "ClojureScript, Reagent"}
       {:el :container
        :id :banking.internet-banking/api-application
        :name "API Application"
        :desc "Provides internet banking functionality via a JSON/HTTPS API."
        :tech "Clojure, Pedestal"}
       {:el :container
        :subtype :database
        :id :banking.internet-banking/database
        :name "Database"
        :desc "Stores the user registration information, hashed authentication credentials, access logs, etc."
        :tech "Datomic"}}}
; external systems
 {:el :system
  :id :banking/mainframe-banking-system
  :external true
  :name "Mainframe Banking System"
  :desc "Stores all the core banking information about customers, accounts, transactions, etc."}
 {:el :system
  :id :banking/email-system
  :external true
  :name "E-mail System"
  :desc "The internal Microsoft Exchange email system."}

 ; Context view relations 
 {:el :request
  :id :banking/personal-customer-uses-internet-banking-system
  :from :banking/personal-customer
  :to :banking.internet-banking/internet-banking-system
  :name "Views account balances and makes payments using"
  :tech "HTTPS"}
 {:el :request
  :id :banking.internet-banking/internet-banking-system-uses-email-system
  :from :banking.internet-banking/internet-banking-system
  :to :banking/email-system
  :name "Sends e-mail using"
  :tech "HTTPS, REST"}
 {:el :request
  :id :banking.internet-banking/internet-banking-system-using-mainframe-banking-system
  :from :banking.internet-banking/internet-banking-system
  :to :banking/mainframe-banking-system
  :name "Gets account information from, and makes payments using"}
 {:el :send
  :id :banking/email-system-sends-mail-to-personal-customer
  :from :banking/email-system
  :to :banking/personal-customer
  :name "Sends e-mail to"
  :tech "SMTP"}} 

Example of a views specification

#{{:el :context-view
  :id :banking/context-view
  :spec {:selection [{:from {:id :banking.internet-banking/internet-banking-system}}
                     {:to   {:id :banking.internet-banking/internet-banking-system}}]
         :include :related
         :plantuml {:sprite-libs [:azure :devicons :font-awesome-5]}}
  :title "System Context View of the Internet Banking System"
  :desc "shows the Internet Banking System and its context"
  :ct [{:ref :banking.email/email-system-sends-mail-to-personal-customer :direction :up}]}

 {:el :container-view
  :id :banking/container-view
  :spec {:selection [{:namespace-prefix "banking.internet-banking"}
                     {:from {:namespace-prefix "banking.internet-banking"}}
                     {:to {:namespace-prefix "banking.internet-banking"}}]
         :include :related
         :plantuml {:sprite-libs [:azure :devicons :font-awesome-5]}}
  :title "Container View of the Internet Banking System"
  :desc "shows the containers of the Internet Banking System and their relations" 
  :ct [{:ref :banking.email/email-system-sends-mail-to-personal-customer :direction :up}]}}

PlantUML export of the System Context View

@startuml context-view
!include <C4/C4_Context.puml>

title System Context View of the Internet Banking System
System_Ext(banking_mainframe_mainframeBankingSystem, "Mainframe Banking System", $descr="Stores all the core banking information about customers, accounts, transactions, etc.")
System(banking_internetBanking_internetBankingSystem, "Internet Banking System", $descr="Allows customers to view information about their bank accounts and make payments.")
System_Ext(banking_email_emailSystem, "E-Mail System", $descr="The internal Microsoft Exchange email system.")
Person(banking_personalCustomer, "Personal Banking Customer", $descr="A customer of the bank, with personal banking accounts.")
Rel(banking_internetBanking_internetBankingSystem, banking_mainframe_mainframeBankingSystem, "gets account information from, and makes payments using")
Rel(banking_internetBanking_internetBankingSystem, banking_email_emailSystem, "sends e-mail using")
Rel(banking_personalCustomer, banking_internetBanking_internetBankingSystem, "views account balances and makes payments using")
Rel_U(banking_email_emailSystem, banking_personalCustomer, "sends e-mail to")
SHOW_LEGEND()
@enduml

System Context View rendered with PlantUML

Container View rendered with PlantUML

![Container View rendered with PlantUM